216600221 has 2 divisors, whose sum is σ = 216600222. Its totient is φ = 216600220.

The previous prime is 216600191. The next prime is 216600227. The reversal of 216600221 is 122006612.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 180768025 + 35832196 = 13445^2 + 5986^2 .

It is a cyclic number.

It is not a de Polignac number, because 216600221 - 2¹⁰ = 216599197 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 216600193 and 216600202.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (216600227) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 108300110 + 108300111.

It is an arithmetic number, because the mean of its divisors is an integer number (108300111).

Almost surely, 2^216600221 is an apocalyptic number.

It is an amenable number.

216600221 is a deficient number, since it is larger than the sum of its proper divisors (1).

216600221 is an equidigital number, since it uses as much as digits as its factorization.

216600221 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 288, while the sum is 20.

The square root of 216600221 is about 14717.3442237382. The cubic root of 216600221 is about 600.5552461961. Note that the first 3 decimals are identical.

Adding to 216600221 its reverse (122006612), we get a palindrome (338606833).

The spelling of 216600221 in words is "two hundred sixteen million, six hundred thousand, two hundred twenty-one".